Ceramic body defect inspecting apparatus and ceramic body defect inspecting method

Abstract

A plurality of illumination elements obliquely irradiating an inspection target region in irradiation directions different from each other and equiangularly spaced around an image capturing part in a state where each of a low-angle, intermediate-angle, and high-angle illumination parts has a different irradiation angle are sequentially turned on and off. An image of the image captured region is captured every time each of the plurality of illumination elements is turned on. A determination image generation part specifies an inspection-excluded region based on at least one of maximum luminance image data and minimum luminance image data of three types of captured image data each corresponding to an irradiation angle of each illumination part and generates determination image data for the image captured region other than the inspection-excluded region. A defect determination part determines existence of a defect based on the determination image data.

The invention claimed is: 
     
       1. A ceramic body defect inspecting apparatus configured to inspect existence of a defect on an outer surface of a ceramic body, the apparatus comprising:
 a table on which a ceramic body as an inspection target is to be placed; 
 an image capturing part configured to capture at least part of an inspection target surface of the ceramic body placed on the table as an image captured region in a normal direction of the inspection target surface; 
 a low-angle illumination part, an intermediate-angle illumination part, and a high-angle illumination part each including a plurality, which is four or more, of illumination elements obliquely irradiating the image captured region with illumination light in irradiation directions different from each other and equiangularly spaced around the image capturing part; 
 a determination image generation part configured to generate determination image data for determining existence of a defect in the image captured region based on captured image data acquired by the image capturing part; and 
 a defect determination part configured to determine existence of a defect based on the determination image data, wherein 
 the plurality of illumination elements included in the low-angle illumination part have an irradiation angle θ0 of 5° to 30°, 
 the plurality of illumination elements included in the intermediate-angle illumination part have an irradiation angle θ1 of 30° to 60°, 
 the plurality of illumination elements included in the high-angle illumination part have an irradiation angle θ2 of 60° to 85°, 
 values of θ0, θ1, and θ2 are different from each other, 
 the plurality of illumination elements are sequentially turned on and off in each of the low-angle illumination part, the intermediate-angle illumination part, and the high-angle illumination part, 
 the image capturing part captures an image of the image captured region every time the plurality of illumination elements in each of the low-angle illumination part, the intermediate-angle illumination part, and the high-angle illumination part are turned on, thereby generating plural pieces of low-angle illumination captured image data, plural pieces of intermediate-angle illumination captured image data, and plural pieces of high-angle illumination captured image data, 
 the determination image generation part includes:
 the maximum/minimum luminance image generation part generating low-angle maximum luminance image data, intermediate-angle maximum luminance image data, and high-angle maximum luminance image data, by respectively synthesizing the plural pieces of low-angle illumination captured image data, the plural pieces of intermediate-angle illumination captured image data, and the plural pieces of high-angle illumination captured image data so that a maximum luminance value for each pixel position in the plural pieces of the synthesized data is set to a luminance value for the pixel position in the generated data, and generating low-angle minimum luminance image data, intermediate-angle minimum luminance image data, and high-angle minimum luminance image data, by respectively synthesizing the plural pieces of low-angle illumination captured image data, the plural pieces of intermediate-angle illumination captured image data, and the plural pieces of high-angle illumination captured image data so that a minimum luminance value for each pixel position in the plural pieces of the synthesized data is set to a luminance value for the pixel position in the generated data; and 
 an excluded region specifying part specifying an excluded pixel region in an image expressed by each of the low-angle minimum luminance image data, the intermediate-angle minimum luminance image data, and the high-angle minimum luminance image data based on at least one of the low-angle maximum luminance image data, the intermediate-angle maximum luminance image data, the high-angle maximum luminance image data, the low-angle minimum luminance image data, the intermediate angle minimum luminance image data, and the high-angle minimum luminance image data, 
 
 the excluded pixel region corresponds to a region not inspected in the image captured region, 
 each of low-angle determination image data, intermediate determination image data, and high-angle determination image data is generated as the determination image data based on the low-angle minimum luminance image data, the intermediate-angle minimum luminance image data, and the high-angle minimum luminance image data disabled for the excluded pixel region, and 
 the defect determination part determines existence of a defect in the image captured region other than the excluded pixel region based on the low-angle determination image data, the intermediate-angle determination image data, and the high-angle determination image data. 
 
     
     
       2. The ceramic body defect inspecting apparatus according to  claim 1 , wherein
 the ceramic body is a honeycomb structural body and the inspection target surface is an end face of the honeycomb structural body, 
 the excluded region specifying part includes at least one of:
 an opening specifying processing part specifying a pixel position in the determination image data for a cell opening at the end face of the honeycomb structural body in the image captured region; 
 a joining part specifying processing part specifying a pixel position in the determination image data for a joining part of a honeycomb segment at the end face of the honeycomb structural body in the image captured region; and 
 an outer part specifying processing part specifying a pixel position in the determination image data for a part outside the honeycomb structural body in the image captured region. 
 
 
     
     
       3. The ceramic body defect inspecting apparatus according to  claim 2 , wherein
 the excluded region specifying part includes the opening specifying processing part, and 
 the opening specifying processing part specifies a pixel region in the determination image data corresponding to the cell opening included in the image captured region as the excluded pixel region based on the low-angle maximum luminance image data or the intermediate-angle maximum luminance image data. 
 
     
     
       4. The ceramic body defect inspecting apparatus according to  claim 2 , wherein
 the excluded region specifying part includes the joining part specifying processing part, and 
 the joining part specifying processing part specifies a pixel region in the determination image data of the joining part included in the image captured region as the excluded pixel region based on the intermediate-angle maximum luminance image data or the high-angle maximum luminance image data. 
 
     
     
       5. The ceramic body defect inspecting apparatus according to  claim 2 , wherein
 the excluded region specifying part includes the outer part specifying processing part, and 
 the outer part specifying processing part specifies a pixel region in the determination image data of the part outside the honeycomb structural body included in the image captured region as the excluded pixel region based on the low-angle minimum luminance image data or the intermediate-angle minimum luminance image data. 
 
     
     
       6. The ceramic body defect inspecting apparatus according to  claim 1 , further comprising
 a luminance correction processing part correcting luminance of the plural pieces of low-angle illumination captured image data, the plural pieces of intermediate-angle illumination captured image data, and the plural pieces of high-angle illumination captured image data, wherein 
 the maximum/minimum luminance image generation part generates the low-angle maximum luminance image data, the intermediate-angle maximum luminance image data, the high-angle maximum luminance image data, the low-angle minimum luminance image data, the intermediate-angle minimum luminance image data, and the high-angle minimum luminance image data based on the plural pieces of low-angle illumination captured image data, the plural pieces of intermediate-angle illumination captured image data, and the plural pieces of high-angle illumination captured image data in which luminance has been corrected by the luminance correction processing part. 
 
     
     
       7. The ceramic body defect inspecting apparatus according to  claim 1 , wherein
 the determination image generation part generates the determination image data as binarized data, and 
 the defect determination part determines that there is a defect in the image captured region when the determination image data includes a dark part having pixels equal to or larger in number than a predetermined threshold. 
 
     
     
       8. The ceramic body defect inspecting apparatus according to  claim 1 , wherein
 each of the plurality of illumination elements in at least one of the low-angle illumination part, the intermediate-angle illumination part, and the high-angle illumination part is made up of at least two dimming units individually dimmable. 
 
     
     
       9. The ceramic body defect inspecting apparatus according to  claim 1 , wherein
 the plurality of illumination elements of each of the low-angle illumination part, the intermediate-angle illumination part, and the high-angle illumination part are supported by one support body, and 
 the plurality of illumination elements of the low-angle illumination part, the plurality of illumination elements of the intermediate-angle illumination part, and the plurality of illumination elements of the high-angle illumination part are arranged in a plane different from each other, respectively. 
 
     
     
       10. The ceramic body defect inspecting apparatus according to  claim 1 , wherein
 the plurality of illumination elements of each of the low-angle illumination part, the intermediate-angle illumination part, and the high-angle illumination part are eight illumination elements. 
 
     
     
       11. A method of inspecting existence of a defect on an outer surface of a ceramic body, the method comprising:
 a placement step of placing a ceramic body as an inspection target on a predetermined table; 
 an image capturing step of generating plural pieces of captured image data by capturing, through predetermined image capturing means, at least part of an inspection target surface of the ceramic body placed on the table as an image captured region in a normal direction of the inspection target surface; 
 a determination image generation step of generating determination image data for determining existence of a defect in the image captured region based on plural pieces of captured image data obtained in the image capturing step; and 
 a defect determination step of determining existence of a defect based on the determination image data, wherein 
 in the image capturing step, a low-angle illumination part, an intermediate-angle illumination part, and a high-angle illumination part each including a plurality, which is four or more, of illumination elements obliquely irradiating the image captured region with illumination light in irradiation directions different from each other and equiangularly spaced around the image capturing part are arranged in a state where: 
 the plurality of illumination elements included in the low-angle illumination part have an irradiation angle θ0 of 5° to 30°; 
 the plurality of illumination elements included in the intermediate-angle illumination part have an irradiation angle θ1 of 30° to 60°; 
 the plurality of illumination elements included in the high-angle illumination part have an irradiation angle θ2 of 60° to 85°; and 
 values of θ0, θ1, and θ2 are different from each other, 
 the image capturing means captures an image of the image captured region every time the plurality of illumination elements in each of the low-angle illumination part, the intermediate-angle illumination part, and the high-angle illumination part are turned on and off, thereby generating plural pieces of low-angle illumination captured image data, plural pieces of intermediate-angle illumination captured image data, and plural pieces of high-angle illumination captured image data, 
 the determination image generation step includes:
 a maximum/minimum luminance image generation step of generating low-angle maximum luminance image data, intermediate-angle maximum luminance image data, and high-angle maximum luminance image data, by respectively synthesizing the plural pieces of low-angle illumination captured image data, the plural pieces of intermediate-angle illumination captured image data, and the plural pieces of high-angle illumination captured image data so that a maximum luminance value for each pixel position in the plural pieces of the synthesized data is set to a luminance value for the pixel position in the generated data, and generating low-angle minimum luminance image data, intermediate-angle minimum luminance image data, and high-angle minimum luminance image data, by respectively synthesizing the plural pieces of low-angle illumination captured image data, the plural pieces of intermediate-angle illumination captured image data, and the plural pieces of high-angle illumination captured image data so that a minimum luminance value for each pixel position in the plural pieces of the synthesized data is set to a luminance value for the pixel position in the generated data; and 
 an excluded region specifying step of specifying an excluded pixel region in an image expressed by each of the low-angle minimum luminance image data, the intermediate-angle minimum luminance image data, and the high-angle minimum luminance image data based on at least one of the low-angle maximum luminance image data, the intermediate-angle maximum luminance image data, the high-angle maximum luminance image data, the low-angle minimum luminance image data, the intermediate angle minimum luminance image data, and the high-angle minimum luminance image data; and 
 
 a generation step of generating each of low-angle determination image data, intermediate determination image data, and high-angle determination image data as the determination image data based on the low-angle minimum luminance image data, the intermediate-angle minimum luminance image data, and the high-angle minimum luminance image data disabled for the excluded pixel region, and 
 the excluded pixel region corresponds to a region not inspected in the image captured region, 
 in the defect determination step, existence of a defect in the image captured region other than the excluded pixel region is determined based on the low-angle determination image data, the intermediate-angle determination image data, and the high-angle determination image data. 
 
     
     
       12. The ceramic body defect inspecting method according to  claim 11 , wherein
 the ceramic body is a honeycomb structural body and the inspection target surface is an end face of the honeycomb structural body, 
 the excluded region specifying step includes at least one of:
 an opening specifying processing step of specifying a pixel position in the determination image data for a cell opening at the end face of the honeycomb structural body included in the image captured region; 
 a joining part specifying processing step of specifying a pixel position in the determination image data for a joining part of a honeycomb segment at the end face of the honeycomb structural body in the image captured region; and 
 an outer part specifying processing step of specifying a pixel position in the determination image data for a part outside the honeycomb structural body in the image captured region. 
 
 
     
     
       13. The ceramic body defect inspecting method according to  claim 12 , wherein
 the excluded region specifying step includes the opening specifying processing step, and 
 in the opening specifying processing step, a pixel position in the determination image data of the cell opening included in the image captured region is specified based on the low-angle maximum luminance image data or the intermediate-angle maximum luminance image data. 
 
     
     
       14. The ceramic body defect inspecting method according to  claim 12 , wherein
 the excluded region specifying step includes the joining part specifying processing step, and 
 in the joining part specifying processing step, a pixel position in the determination image data of the joining part included in the image captured region is specified based on the intermediate-angle maximum luminance image data or the high-angle maximum luminance image data. 
 
     
     
       15. The ceramic body defect inspecting method according to  claim 12 , wherein
 the excluded region specifying step includes the outer part specifying processing step, and 
 in the outer part specifying processing step, a pixel position in the determination image data of the part outside the honeycomb structural body included in the image captured region is specified based on the low-angle minimum luminance image data or the intermediate-angle minimum luminance image data. 
 
     
     
       16. The ceramic body defect inspecting method according to  claim 11 , further comprising
 a luminance correction processing step of correcting luminance of the plural pieces of low-angle illumination captured image data, the plural pieces of intermediate-angle illumination captured image data, and the plural pieces of high-angle illumination captured image data, wherein 
 in the maximum/minimum luminance image generation step, the low-angle maximum luminance image data, the intermediate-angle maximum luminance image data, the high-angle maximum luminance image data, the low-angle minimum luminance image data, the intermediate-angle minimum luminance image data, and the high-angle minimum luminance image data are generated based on the plural pieces of low-angle illumination captured image data, the plural pieces of intermediate-angle illumination captured image data, and the plural pieces of high-angle illumination captured image data in which luminance has been corrected in the luminance correction processing step. 
 
     
     
       17. The ceramic body defect inspecting method according to  claim 11 , wherein
 in the generation step, the determination image data is generated as binarized data, and 
 in the defect determination step, it is determined that there is a defect in the image captured region when the determination image data includes a dark part having pixels equal to or larger in number than a predetermined threshold. 
 
     
     
       18. The ceramic body defect inspecting method according to  claim 11 , wherein
 each of the plurality of illumination elements in at least one of the low-angle illumination part, the intermediate-angle illumination part, and the high-angle illumination part is made up of at least two dimming units individually dimmable, and 
 luminance difference in accordance with difference between distances from at least one of the plurality of low-angle illumination elements, the plurality of intermediate-angle illumination elements, and the plurality of high-angle illumination elements in a capturing range of the image capturing means is reduced by individually dimming the at least two dimming units in advance before image capturing by the image capturing means in the image capturing step. 
 
     
     
       19. The ceramic body defect inspecting method according to  claim 11 , wherein
 the plurality of illumination elements of each of the low-angle illumination part, the intermediate-angle illumination part, and the high-angle illumination part are eight illumination elements.